Medcyclopaedia is free for non-commercial uses and contains 10,000 images:
The Standard Edition of Medcyclopaedia™ includes all text and images from The Encyclopaedia of Medical Imaging's eight book volumes: Physics, Techniques and Procedures, Normal Anatomy, Musculoskeletal and Soft Tissue Imaging, Gastrointestinal and Urogenital Imaging, Chest and Cardiovascular Imaging, Neuroradiology and Head and Neck Imaging, and Paediatric Imaging.
You are free to copy text and images for non-commercial use in lectures, articles, etc. provided that you refer to the source.
Link from Insurance Defense Blog.